ESTRO 2024 - Abstract Book

S1488

Clinical - Lower GI

ESTRO 2024

2. Ogawa S, Hida J ichi, Ike H, Kinugasa T, Ota M, Shinto E, et al. Selection of Lymph Node–Positive Cases Based on Perirectal and Lateral Pelvic Lymph Nodes Using Magnetic Resonance Imaging: Study of the Japanese Society for Cancer of the Colon and Rectum. Ann Surg Oncol. 2016;23(4):1187–94.

3. Otero de Pablos J, Mayol J. Controversies in the Management of Lateral Pelvic Lymph Nodes in Patients With Advanced Rectal Cancer: East or West? Front Surg. 2020;6(January):1–8.

4. Meldolesi E, Chiloiro G, Giannini R, Menghi R, Persiani R, Corvari B, et al. The Role of Simultaneous Integrated Boost in Locally Advanced Rectal Cancer Patients with Positive Lateral Pelvic Lymph Nodes. Cancers (Basel). 2022;14(7). Ogura A, Konishi T, Cunningham C, Garcia-Aguilar J, Iversen H, Toda S, et al. Neoadjuvant (chemo)radiotherapy with total mesorectal excision only is not sufficient to prevent lateral local recurrence in enlarged nodes: Results of the multicenter lateral node study of patients with low ct3/4 rectal cancer. J Clin Oncol. 2019;37(1):33–43. 6. Kim TH, Jeong SY, Choi DH, Kim DY, Jung KH, Moon SH, et al. Lateral lymph node metastasis is a major cause of locoregional recurrence in rectal cancer treated with preoperative chemoradiotherapy and curative resection. Ann Surg Oncol. 2008;15(3):729–37. 5.

612

Digital Poster

Pathological CR rate with SIB for rectal cancer with short course preoperative Radiotherapy.

Thuraya Al-Hajri 1 , Ahmed Al-Habsi 1 , Rupa Das 1 , Balaji Subramanian 2

1 Royal hospital, Radiation Oncology, Msucat, Oman. 2 Royal hospital0, Radiation Oncology, Msucat, Oman

Purpose/Objective:

To assess if escalating the radiation dosage to the rectal tumor using simultaneous integrated boost during preoperative short course radiotherapy would enhance the rate of pathological complete response.

Material/Methods:

Rectal cancer patients who were eligible for RAPIDO protocol from 2021 to 2023 received 25Gy to the pelvis and extra 5 Gy as simultaneous integrated boost ( SIB) using VMAT planning to the GTV alone. Pathological complete response and Toxicity were evaluated

Results:

In total, 25 patients were identified with locally advanced rectal cancer that had undergone preoperative short course radiotherapy followed by chemotherapy and total mesorectal excision. Main histology was Moderately differentiated adencarcinoma . The mean tumor distance was 6 cm (6-13 cm) from anal verge. The planned radiation was a standard dose of 25 Gy in 5 fractions to the primary tumor and lymphatics at-risk. The dose escalation was achieved via SIB delivering 30 Gy to the tumor GTV. All patients were treated with volumetric